none were stable on my craptop
only used 8.1.1.12 and the betas on my desktop, mostly not too bad but found the hair behaves better in recently installed on my desktop C6pro! but it is terribly slow!
Carrara is more stable than a lot of other programs I use, inc Daz studio and iClone!

It crashes seldom - eg when i drag a figure in the hierachy and parent it to something else,
but MIANLy when I am in the texture room and I start to close all my texture windows and still have the refresh buton ticked.
This is a guaranteed crash most times.
It also has a hissy fit if I smooth a model and then debone it (Ie get rid of the skeleton) and the scene is very large say around 1.gig

I installed one of the 8.5 betas and it screwded^%*&%$#$# my runtime so I refuse to be a beta tester after that - my time and work is too valuable to lose.

I normally use C8.1.1.12 , and that seems to be pretty good for modelling texturing animating and rendering.
I still jump in and out of the 8.5 beta's to test stuff.
plus C6 and C7.2 for testing backward compatibility